Antiperspirant compositions normally contain an astringent, such as aluminum chlorhydrate, which chemically suppresses the production of perspiration by sweat glands. This astringent is commonly applied on the skin in the form of an aerosol spray.
The antiperspirant active compound is suspended as a dry, impalpable powder in a liquid vehicle together with a non-aqueous liquified volatile propellant in a pressurized aerosol container. The aerosol spray is produced by rapid boiling of the propellant as it dispenses from the atomizing valve of the aerosol container.
The aerosol method of application has gained wide acceptance for a number of reasons. Aerosol application of an antiperspirant salt in the form of a powder suspended in the propellant is cosmetically desirable because the antiperspirant can be smoothly and effectively applied to the skin in a manner that feels dry and comfortable. Furthermore, because the antiperspirant powder does not dissolve in the liquified propellant medium, the antiperspirant salt does not corrode ordinary metal aerosol cans.
One difficulty associated with antiperspirant aerosol sprays is that the delivery of small particles of antiperspirant active compound in a finely divided spray can readily clog small valve orifices. When a residue of the liquid propellant/aerosol composition mixture remains in the valve passages following a squirt, evaporation of the liquid may lead to deposition of solid material and consequent valve clogging.
Another problem associated with conventional antiperspirant aerosol sprays is that they utilize a large amount of propellant gas. However, an aerosol composition having a high proportion of propellant is undesirable. Fluorocarbon propellants are believed to accumulate in the stratosphere, where they interfere with the protective ozone layer. In addition to contributing to air pollution, hydrocarbon propellants are flammable, requiring that the proportion of hydrocarbons be restricted to avoid a fire hazard.
Conventional antiperspirant aerosol sprays typically contain the following components: particles of an antiperspirant active compound; a suspending agent to prevent the particles of antiperspirant active compound from settling out; an emollient carrier liquid for carrying the antiperspirant particles from the container to the skin in the form of a moist spray rather than a dusty cloud to improve adherence of the antiperspirant particles to the skin; and a propellant for expelling these components from the container. Other minor additives, such as fragrance or medicant are optional.
For example, U.S. Pat. No. 3,288,681 to Goldberg et al. discloses an antiperspirant powder aerosol composition comprising an aluminum compound, e.g., aluminum chlorhydrate, alcohol, propellant and an emollient carrier, e.g., isopropyl myristate or palmitate.
U.S. Pat. No. 3,395,214 to Mummert discloses a relatively dry, collapsible foam in which an active antiperspirant material is suspended. The antiperspirant material, e.g., aluminum salt, is dispersed in a nonvolatile carrier, e.g., isopropyl myristate, with a volatile solvent, e.g., alcohol, and water to form a base. This base is then combined with a sufficient amount (10-15 wt. %) of liquified propellant. Allantoin is added to minimize irritation to skin sensitive to an aluminum based product.
U.S. Pat. No. 3,773,683 to Aubert discloses a process for preparing a propellant containing a bulking or suspending agent selected from the group of montmorillonite clays, e.g., Bentone-38. A polar liquid, e.g., propylene carbonate, is used to aid in obtaining maximum dispersion efficacy.
U.S. Pat. No. 3,792,068 to Luedders et al. discloses a powder antiperspirant active complex comprising astringent aluminum salt and zirconium salt for incorporation into powder aerosol antiperspirant compositions. One suitable suspending agent is Bentone-38. The carrier liquid may be, e.g., isopropyl palmitate, di-n-butyl phthalate, or silicone oils such as dimethylpolysiloxane.
U.S. Pat. No. 4,045,548 to Luedders et al. discloses a powder aerosol antiperspirant compositions wherein the preferred antiperspirant compound is aluminum chlorhydroxide and the preferred emollient-carrier agent is di-isopropyl adipate.
U.S. Pat. Nos. 4,053,581 and 4,073,880 to Pader et al. and 4,065,564 to Miles, Jr. et al. disclose an antiperspirant solution containing nonvolatile siloxane liquid, volatile polydimethyl siloxane liquid or both added to an alcohol solution of an aluminum chlorhydroxide complex. The siloxane reduces the tackiness of the aluminum chlorhydroxide complex during drying while substantially reducing clogging of the pump spray valve.
U.S. Pat. No. 4,110,428 to Kuhn et al. discloses an aerosol antiperspirant composition in which an antiperspirant agent, e.g., aluminum chlorhydrate, is suspended in a propellant medium containing a polyalkylene glycol to reduce staining of clothing which is accidentally exposed to the antiperspirant.
U.S. Pat. Nos. 4,078,051, 4,080,438 and 4,080,439 to Pomot et al. disclose an antiperspirant agent comprising microcrystals of an aluminum compound coated with degraded starch to provide an atomizable gel. Representative starches are waxy or ordinary corn starches degraded by acid hydrolysis.
U.S. Pat. No. 4,174,386 to Spitzer et al. discloses an aerosol antiperspirant composition comprising an astringent salt, a liquified propellant, a nonvolatile miscible organic liquid, a bulking agent and a solid aliphatic carboxylic acid to enhance adherence of the antiperspirant salt to the skin.
U.S. Pat. No. 4,278,655 to Elmi discloses an aerosol antiperspirant composition comprising an active antiperspirant salt, a hydrophobic suspending agent, a liquid carrier and a liquified propellant. In place of conventional liquid carriers such as volatile silicone, isopropyl palmitate and isopropyl myristate, benzoic acid esters are used.
U.S. Pat. No. 4,806,338 to Smith discloses an antiperspirant aerosol composition comprising 1-40% of a particulate antiperspirant material, 0.005-6.0% of a functionalized siloxane and 60-95% of an aerosol propellant. The compositions also contain a silicone gum material and a volatile silicone oil, i.e., cyclomethicone.
U.S. Pat. Nos. 4,840,786 and 4,904,463 to Johnson et al. disclose an antiperspirant aerosol composition comprising 2-10% of a hydrophobic liquid, 20-95% of a propellant, 2-30% of an enhanced efficacy metallic antiperspirant material, 0.1-3.0% of a hydrophobically treated clay suspension agent and 0.01-0.2% of an activator, such as propylene carbonate, that enables the hydrophobically treated clays to suspend the antiperspirant active compound in the hydrophobic liquid carrier.
U.S. Pat. No. 4,889,711 to Kai et al. discloses an antiperspirant aerosol composition comprising a mixed powder phase, a mixed oil phase and in excess of 90 wt. % propellant. The mixed oil phase comprises, for example, isopropyl myristate, cyclic dimethyl siloxane, bactericide and perfume. The mixed powder phase comprises aluminum hydroxychloride and a silicone-treated clay mineral. This patent also discloses comparative compositions having aluminum hydroxychloride and talc which has not been treated with silicone.
U.S. Pat. No. 4,935,224 to Russo et al. discloses an antiperspirant aerosol composition comprising an active antiperspirant salt, a silicone polymer (e.g., a silicone gum), a volatile low-viscosity fluid in which the silicone polymer is soluble (i.e., cyclomethicone) and a propellant.
Finally, U.S. Pat. No. 4,822,596 to Callingham et al. discloses an antiperspirant composition dispensed from an aerosol container which absorbs perspiration at the skin surface. The antiperspirant composition comprises a moisture-absorbent polymer in powder form, e.g., chemically modified starches. This patent also discloses that a perspiration depressant such as aluminum chlorhydrate can be incorporated along with the moisture-absorbent polymer.
The prosecution file history of the Callingham patent explicitly states that Dry Flo chemically modified corn starch does not have the moisture-absorbency properties required by the invention disclosed in that patent. In support of this thesis, Callingham et al. cited UK Patent No. 1453202, owned by Colgate-Palmolive Company, which discloses an antiperspirant composition which includes 91.54% propellant mixture, 3% aluminum chlorhydrate, 4.0% propylene glycol dipelargonate, 0.2% Bentone 38, 1.0% Dry Flo starch, 0.06% propylene carbonate, and 0.2% perfume (see Example 6). This British patent also discloses that the amount of liquid propellant can vary between 50 and 98 wt. %.
None of the patents discussed above disclose a specific formulation of an antiperspirant aerosol composition in which the amount of propellant is reduced to less than or equal to 60 wt. % by raising the particulate solids content of the composition to 10-35 wt. %. Therefore these conventional compositions are disadvantageous because greater amounts of hydrocarbons or fluorocarbons are released into the atmosphere, thereby contributing to air pollution.